Diagnostically:

CBC: Not suggestive of severe systemic infectious process.

Urinalysis consistent with urinary tract infection

Pregnancy test negative

MDM:

Suspect unilateral flank pain.

Most likely pyelonephritis given his urine analysis findings, pain over the kidney region, and constellation of systemic signs of infection.

Considered pregnancy-related complications however urine pregnancy is negative thereby making this sufficiently unlikely.

Considered possible nephrolithiasis however history of constant pain, noncolicky, no history of kidney stones and no gross hematuria in urine analysis, this diagnosis is sufficiently unlikely to warrant further diagnostics at this time.

Considered alternatives organ systems-specifically musculoskeletal back pain however given history as above and pain reproducible over the kidney area and no muscular tenderness, suspect most likely musculoskeletal pain.

Considered neurological cord or spinal pathology however there is no midline spinal pain and patient is neurologically intact and patient has no signs or symptoms of cauda equina. Therefore does not meet threshold for further diagnostics at this time.

Considered possible sexually transmitted infection however patient has no significant symptomatology consistent with sexually transmitted infection and patient does not have high risk sexual risk features on history. Discussed risks and benefits with patient for pelvic exam and patient deferred pelvic exam and emergency department.

On reevaluation, pain is adequately controlled, patient is tolerating by mouth fluids. Given patient has no significant comorbidities that would preclude outpatient antibiotic treatment for pyelonephritis, the patient is appropriate for outpatient care. Advised to return precautions-specifically for inability to tolerate by mouth fluids, inability to tolerate by mouth antibiotics.